| 摘要 |
A video-input stream to a personal computer (PC) is converted from YUV format to RGB format. Two look-up tables are used. One look-up table has the Y and V components as address inputs, while the other look-up table has Y and U components as address inputs. The address inputs select one data word in the table for the Y,V or Y,U pair. Each data word contains an exact conversion to either the red component R or the blue component B since the result of the functions R=Y+1.371*V is stored in one table while the result of the function B=Y+1.732*U is stored in the other table. Each table also contains a partial green component in each data word. The Y,U table contains the result of the partial-green function (Y/2-0.698*V) in each data word, while the other table contains the result of the partial-green function (Y/2-0.336*U). An adder adds the two partial-green results from the two tables to produce the green component G. Clipping of color components to a defined range is included in the tables because the data words stored are the clipped results. Since each table has only two of the YUV components as inputs rather than all three, the size of the table is greatly reduced, even though the results are exact and not approximated. Only one add and no multiplies are required, reducing processor loading.
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